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8C2*6C2*4C2*2C2 = 2520 ways 8 people will form 4 teams of 2 each
My guess is we need to divide this number by 4C2 (two teams from 4 possible teams can play a game of doubles) ...
Hence, 2520/4C2 = 2520/6 = 420

Thats the only explanation I can think of... I must admit initially I thought the answer was 2520 too...

If you pick one player, he has 7 possible partners.
We have six left, if we pick one, he has 5 possible partners.
We have four, if we pick one, he has 3 different possible partners,

If you pick one player, he has 7 possible partners. We have six left, if we pick one, he has 5 possible partners. We have four, if we pick one, he has 3 different possible partners,

Therefore 7*5*3=105

Its difficult for me to understand.

If you pick one player, he has 7 possible partners.

here, first player could be picked from pool of 8 people each having 7 remaining people as partner. All combinations seems 8*7 rather than just 7. Dont know what I am missing.

Order isnt imp and isnt that the reason why we have used combination instead of Permutation here??? why do we need to divide the outcome by 4! pls explain.....

There's two things going on here:
(1) ordering between members in a team.
(2) ordering between teams

In this question order is NOT relevant on both counts. Using combinations ensures ordering between members is excluded.
Dividing by 4! makes sure ordering between teams is also excluded.
I hope this helps

There's two things going on here: (1) ordering between members in a team. (2) ordering between teams

In this question order is NOT relevant on both counts. Using combinations ensures ordering between members is excluded. Dividing by 4! makes sure ordering between teams is also excluded. I hope this helps

thanks sadsack for clearing the confusion... its a great help indeed!

With that one, it's painfully obvious that I'm totally lost with permutations and combinations. Anybody got any suggestions? I've gone through the GMAT club course material, and a couple of other books too. Still my mind just refuses to think in the proper way!!!

Order isnt imp and isnt that the reason why we have used combination instead of Permutation here??? why do we need to divide the outcome by 4! pls explain.....

I had the same problem Tingle. This was my issue. thanks sadsack for the clear post.

anandsebastin> I too am completely dumbfounded when it comes to these thypes of problems, which is exactly why I keep posting them over and over again, scrutinizing the methodology. Have you checked out the book VeritasProject GMAT yet? I have heard that they really drill in this subject matter.